JP7374159B2 - Thermal power plants and control methods for thermal power plants - Google Patents

Description

The present invention relates to a thermal power plant that utilizes steam generated in a boiler and a method of controlling the thermal power plant.

2. Description of the Related Art A thermal power plant that drives a steam turbine using steam generated in a boiler (steam generator) is known. This type of thermal power plant has conventionally served as a large-scale power source in the electric power system, mainly serving as base load, and together with the load fluctuation response capability of GTCC (gas turbine combined cycle) plants, has contributed to the stable supply of domestic electricity.

By the way, with the recent increase in the amount of electricity derived from renewable energy being connected to the power system, the proportion of power transmitted by thermal power plants and GTCC plants in the daytime power system is decreasing year by year, and in some regions, the amount of power transmitted by these plants is decreasing. Although it is now necessary to reduce the number of operating units to the minimum necessary level to maintain the frequency of the power grid and adjust supply and demand, there is still a possibility that electricity derived from renewable energy that is in surplus may be refused connection to the power grid. There is.

In order to further expand renewable energy-derived electricity into the power system, it is necessary to use a conventional large-scale power source that requires a large amount of power to be transmitted at the lowest load of the plant, and the time required to restart the plant during DSS (daily startup/shutdown) operation. It is essential to improve the operability of thermal power plants, which have a long period of time.

Utility Model Publication No. 64-54605

Patent Document 1 mentioned above stores a part of the feed water in a hot water tank during low-load plant operation, releases the hot water to a group of high-pressure feed water heaters during peak power demand, and controls the extraction of air to the high-pressure feed water heaters. This is intended to increase the output of the steam turbine by cutting or reducing it.

On the other hand, the low-load operation of the plant in Patent Document 1 is based on the premise that the entire amount of main steam and reheated steam generated in the boiler is introduced into the steam turbine through the governor to generate electricity, which can be realized in a thermal power plant. The minimum load is the amount of heat generated in the main steam and reheated steam generated at the minimum load of the boiler minus the extracted air in the turbine, and is generally 25% load, and even in the minimum case, the power is 10% load or more. It was necessary to transmit power to the grid.

By making it possible to reduce the power sent from coal-fired power plants (thermal power plants) to the power grid from the conventional minimum load of 10% to almost 0% load (parallel non-transmission operation), In addition to expanding the range of renewable energy that can be accepted into the power system of It is hoped that the amount of power transmitted will quickly increase in response to the decrease in the amount of power generated, contributing to maintaining the frequency of the power supply system and adjusting supply and demand.

In addition, in thermal power plants that have conventionally used diesel oil as startup fuel and operated under DSS, by making it possible to operate the plant continuously using inexpensive coal, we aim to reduce fuel costs and operate DSS. It is desired to avoid equipment wear and tear associated with this, as well as troubles during startup.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal power generation technology that can flexibly respond to changes in the amount of renewable energy generated while maintaining high operability.

The present invention includes a boiler, a steam turbine driven by steam from the boiler, a turbine bypass line for sending steam bypassing the steam turbine, and a turbine bypass line for cooling the exhaust gas of the steam turbine and generating condensate. A thermal power plant comprising: a water heater; a low-pressure feedwater heater that heats the condensate with extracted steam from the steam turbine; and a deaerator that degasses the condensed water with the extracted steam, a hot water heater that uses the main steam of the turbine bypass line as a heat source and the condensate supplied from the condenser as high-temperature water; a high-temperature water tank that stores the high-temperature water; and a high-temperature water tank that stores the high-temperature water. The apparatus is characterized by comprising a high-temperature water pump that sends high-temperature water to the downstream of the low-pressure feed water heater or to the deaerator.

According to the present invention, it is possible to provide thermal power generation technology that can flexibly respond to changes in the amount of renewable energy generated while maintaining high operability.

1 is a schematic configuration diagram of a thermal power plant according to an embodiment. 1 is a schematic configuration diagram of a thermal power plant similar to one embodiment. 1 is an example of an operation during heat storage operation of a thermal power plant according to an embodiment. 1 is an example of an operation during heat dissipation operation of a thermal power plant according to an embodiment. FIG. 1 is a schematic configuration diagram showing the range of a water heat storage system according to an embodiment. FIG. 1 is a schematic configuration diagram for explaining an auxiliary steam line of a thermal power plant according to an embodiment. FIG. 1 is a schematic configuration diagram of a control device for a thermal power plant according to an embodiment. It is a schematic block diagram of the thermal power plant based on the modification 1 of one embodiment. It is a schematic block diagram of the relevant part of the thermal power plant based on the modification 2 of one embodiment. It is a flowchart of the confluence switching process of the thermal power plant based on the modification 2 of one embodiment. It is an explanatory view for explaining partial water passage of the thermal power plant concerning modification 3 of one embodiment. It is a schematic block diagram of the relevant part of the thermal power plant based on the modification 4 of one embodiment. FIG. 7 is an explanatory diagram for explaining heat storage operation of a thermal power plant according to modification 4 of an embodiment. FIG. 7 is an explanatory diagram for explaining heat radiation operation of a thermal power plant according to modification 4 of an embodiment. It is a schematic block diagram of the relevant part of the thermal power plant based on the modification 5 of one embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, and are merely illustrative examples. do not have.
For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained.
For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state.
For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed.
On the other hand, the expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

In the following embodiment, a thermal power plant 1 will be described as an example of a coal-fired thermal power plant that is at least one embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a thermal power plant 1 according to an embodiment.

Thermal power plant 1 includes a boiler 2, a steam turbine 4, a condenser 13, a water heat storage system 70, and a control device 80 (see FIG. 7). In the present embodiment, the thermal power plant 1 includes a high-pressure turbine 4A, an intermediate-pressure turbine 4B, and a low-pressure turbine 4C as the steam turbines 4, but the thermal power plant 1 includes one or two steam turbines 4. or four or more steam turbines 4.

The boiler 2 is a steam generator capable of generating superheated steam by exchanging heat generated by burning pulverized fuel with water and steam. The boiler 2 is, for example, a coal-fired (pulverized coal-fired) boiler that uses pulverized coal obtained by pulverizing coal (carbon-containing solid fuel) as pulverized fuel and burns this pulverized fuel with a burner.

In this embodiment, a coal-fired boiler is exemplified as the boiler 2, but the boiler 2 may use solid fuel such as biomass fuel, PC (petroleum coke) fuel generated during oil refining, or petroleum residue. You may. In addition, the boiler 2 can use not only solid fuel as fuel, but also petroleum such as heavy oil, light oil, and heavy oil, and liquid fuel such as factory waste liquid.Furthermore, gaseous fuel (natural gas, (by-product gas, etc.) can also be used. Furthermore, the boiler 2 may be a co-fired boiler that uses a combination of these fuels.

Steam (superheated steam) generated in the boiler 2 is supplied to the steam turbine 4 via the main steam line 6. In this embodiment, the steam from the boiler 2 is first supplied to the high-pressure turbine 4A provided on the upstream side, thereby driving the high-pressure turbine 4A.

The steam that has finished its work in the high-pressure turbine 4A is reheated in the reheater 35 via the reheat steam line 9, and then supplied to the intermediate-pressure turbine 4B provided on the downstream side. to drive. Reheat steam line 9 connects between high pressure turbine 4A and intermediate pressure turbine 4B. The steam that has completed its work in the intermediate pressure turbine 4B is supplied to the low pressure turbine 4C provided on the downstream side via the intermediate pressure turbine exhaust line 12, thereby driving the low pressure turbine 4C. The intermediate pressure turbine exhaust line 12 connects between the intermediate pressure turbine 4B and the low pressure turbine 4C. The steam that has completed its work in the low-pressure turbine 4C is discharged to the condenser 13, thereby generating condensate.

Further, a turbine bypass line 7 connecting the main steam line 6 and the condenser 13 is provided. The turbine bypass line 7 is provided with a turbine bypass valve 8, and by adjusting the opening degree of the turbine bypass valve 8, a part of the steam flowing through the main steam line 6 bypasses the steam turbine 4 and is condensed. It can be discharged into a container 13.

The output shafts of the high-pressure turbine 4A, intermediate-pressure turbine 4B, and low-pressure turbine 4C are connected to the rotating shaft of the generator 5. The generator generates electricity by being driven by the power from these steam turbines 4. The electric power generated by the generator is supplied to a power system (for example, a commercial system) via a power transmission line (not shown).

Note that the high-pressure turbine 4A, the intermediate-pressure turbine 4B, and the low-pressure turbine 4C have a common output shaft, and the output shaft may be connected to a common generator, or the high-pressure turbine 4A and the low-pressure turbine 4C may be connected to a common generator. It may include a first generator to which the output shaft of the intermediate pressure turbine 4B is connected and a second generator to which the output shaft of the low pressure turbine 4C is connected.

Further, as shown by thick lines in FIG. 6, the steam extracted from the high-pressure turbine 4A and the intermediate-pressure turbine 4B (extracted steam; hb, ib) is transferred to the second high-pressure feedwater heater 21 and the first high-pressure feedwater heater, respectively. 20. A portion of the exhaust steam (he) of the high-pressure turbine 4A is also supplied to the second high-pressure feedwater heater 21. Saturated drain (condensed from extracted steam hb and exhaust steam he) discharged from the second high-pressure feedwater heater 21 is supplied to the first high-pressure feedwater heater 20. Drain discharged from the first high-pressure feedwater heater 20 (condensed saturated drain and extracted steam ib discharged from the second high-pressure feedwater heater 21) is supplied to the deaerator 17. Further, a part of the exhaust steam (ie) of the intermediate pressure turbine 4B is supplied to the deaerator 17. Further, steam extracted from the low pressure turbine 4C (low pressure extracted air; lb) is supplied to the low pressure feed water heater 16. Saturated drain (condensed low pressure bleed air lb) discharged from the low pressure feed water heater 16 is supplied to the condenser 13. Hereinafter, in order to avoid complexity, auxiliary steam lines from each steam turbine 4 to each high-pressure feedwater heater 21, 20 and low-pressure feedwater heater 16 are omitted as appropriate in each figure.

The condensate generated in the condenser 13 is pressurized by the condensate pump 14, supplied to the low-pressure feed water heater 16 via the condensate line 15, and heated with extracted steam (lb) from the low-pressure turbine 4C. It then flows into the deaerator 17. In the deaerator 17, condensate is degassed by a portion of the exhaust steam (ie) of the intermediate pressure turbine 4B. The pressure of the condensate degassed by the deaerator 17 is increased by the feed water pump 18, and the water is supplied to the first high pressure feed water heater 20 and the second high pressure feed water heater 21 via the water supply line 19, and is extracted from the intermediate pressure turbine 4B. The steam (ib) flows into the boiler 2 after being heated by the extracted steam and exhaust steam (hb, he) of the high-pressure turbine 4A.

Boiler 2 is operated in a subcritical state under low load conditions. At this time, the brackish water mixture at the furnace outlet of the boiler 2 is separated into brackish water by a water drain separator 31, steam is sent to a superheater 36, and saturated drain is sent to a condenser via a water drain separator drain line 33 and a water drain separator drain control valve 32. 13.

Next, the water heat storage system 70 provided in the thermal power plant 1 will be explained. The thermal power plant 1 of this embodiment performs low load operation. The low-load operation is an operation in which the boiler 2 and the steam turbine 4 are each subjected to the minimum load. For example, the boiler 2 is lowered to 15% of its minimum output, the output of the steam turbine 4 is lowered to 5%, and all of the output of the steam turbine 4 is used for internal power. As a result, the generator circuit breaker is closed and the power transmission is set to 0 while maintaining the state of connection to the grid, thereby realizing so-called grid non-transmission operation (parallel non-transmission operation).

The water heat storage system 70 of this embodiment corresponds to an output of 10%, which is the difference between, for example, 15% of the minimum load of the boiler 2 and 5% of the load of the steam turbine 4, which occurs during low-load operation. The above heat is stored as high temperature water. Specifically, during low-load operation, the main steam of the turbine bypass line 7 is used as a heat source to heat condensate supplied from the condenser 13 and store it as high-temperature water. Then, during subsequent heat dissipation operation (during high load operation), the stored high temperature water is supplied to the deaerator.

Thereby, the water heat storage system 70 realizes a reduction in the power transmitted to the system of the thermal power plant 1 over a long period of time. Furthermore, the water heat storage system 70 realizes cutting of low pressure bleed air (lb) from the steam turbine 4 to the low pressure feed water heater 16 during high load operation after low load operation. By cutting the low pressure bleed air (lb), it is possible to increase the output of the steam turbine 4 corresponding to the amount of heat of the cut low pressure bleed air (lb). Alternatively, since the boiler steam flow rate corresponding to the increased output of the steam turbine 4 is reduced, the amount of fuel input to the boiler 2 can be reduced. Hereinafter, details of the water heat storage system 70 of this embodiment that realizes this will be explained.

The water heat storage system 70 includes a hot water heater 51, a high temperature water pump 52, a high temperature water tank 53, and a low temperature water tank 59, as shown by the thick line in FIG. The high temperature water pump 52 includes a first high temperature water pump 52A and a second high temperature water pump 52B. The water heat storage system 70 also includes a heat storage steam line 55, a heat storage drain line 57, a low temperature water supply line 49, a low temperature water storage line 58, and a makeup water line 60.

The heat storage steam line 55 is a line that supplies steam passing through the turbine bypass line 7 branched from the main steam line 6 to the hot water heater 51, and includes a heat storage steam flow rate control valve 54. The heat storage drain line 57 is a line that supplies the saturated drain separated by the water drain separator 31 to the hot water heater 51, and includes a heat storage drain flow rate control valve 56.

The low temperature water supply line 49 is a line that branches from the condensate line 15 for supplying condensate supplied from the condensate pump 14 to the hot water heater 51, and includes a low temperature water flow rate control valve 50.

The hot water heater 51 brings the inflowing main steam and saturated drain into contact with the supplied low-temperature water to generate high-temperature water. The generated high-temperature water is, for example, 140°C. The hot water heater 51 is, for example, a direct-contact feed water heater that mixes and heats incoming condensate (low-temperature water), main steam, and saturated drain.

The water heat storage system 70 shown in FIGS. 1 and 5 includes, as the high temperature water pump 52, a first high temperature water pump 52A and a second high temperature water pump 52B. The first high temperature water pump 52A sends high temperature water generated by the hot water heater 51 to the high temperature water tank 53. The second high-temperature water pump 52B sends high-temperature water stored inside the high-temperature water tank 53 to the deaerator 17. Note that the high-temperature water may be supplied to the deaerator 17 alone, or may be combined with the low-pressure feed water at the outlet of the low-pressure feed water heater 16 and then supplied.

Note that the first high-temperature water pump 52A and the second high-temperature water pump 52B do not necessarily need to be placed separately, and one or more high-temperature water pumps 52 having the roles of both may be installed, and the hot water heater 51 and the high-temperature It is also possible to connect the outlet lines of the water tank 53 to the inlets of the high-temperature water pumps 52 and switch them as appropriate.

The high temperature water tank 53 is a tank that stores high temperature water generated by the hot water heater 51. Since the high temperature water stored inside the high temperature water tank 53 is approximately 140°C, the high temperature water tank 53 needs to have a structure that can withstand the saturated vapor pressure of such high temperature water, and the high temperature water stored Adequate insulation must be provided to minimize heat loss from the water. Note that the capacity of the high-temperature water tank 53 may be arbitrarily determined at the design stage depending on the daily low-load operation time required of the thermal power plant 1.

The low temperature water storage line 58 is a line for supplying condensate supplied from the condensate pump 14 to the low temperature water tank 59. The supplied condensate is stored in a low temperature water tank 59.

The make-up water line 60 is a line for supplying low-temperature water stored in the low-temperature water tank 59 to the condenser 13.

The low-temperature water tank 59 is a tank that stores surplus water in the condenser 13 as make-up water to the condenser 13. In this embodiment, the water storage amount is equal to or greater than the water storage amount of the high temperature water tank 53.

As shown in FIG. 7, the control device 80 receives instructions from the outside (such as a control console 81 placed in the power plant) or receives various sensors installed in the thermal power plant 1, including a temperature sensor and a water level sensor. The opening and closing of each control valve (valve) in the thermal power plant 1 is controlled according to signals from the thermal power plant 1. The control valve is controlled to open and close, for example, according to heat storage operation (low load operation) and heat radiation operation (high load operation), which will be described later. The control device 80 also controls the output of each pump. The control device 80 includes, for example, a CPU, a memory, and a storage device, and achieves the above control by having the CPU load a program stored in the storage device in advance into the memory and execute it.

Note that the thermal power plant 1 may bypass the steam turbine 4 and discharge a portion of the steam flowing through the reheat steam line 9 to the condenser 13, as in the thermal power plant 1 shown in FIG. . In this case, the turbine bypass line 7 is connected to the outlet of the high-pressure turbine 4A of the reheat steam line 9, and the low-pressure turbine bypass line 10 is branched from the inlet upstream of the intermediate-pressure turbine 4B of the reheat steam line 9 to form a low-pressure turbine bypass valve. 11 to the condenser 13.

<Heat storage operation>
FIG. 3 shows the heat storage operation of the thermal power plant 1, that is, the storage form of high-temperature water during low-load operation. During low load operation, the amount of main steam generated in the boiler 2 is greater than the amount of main steam consumed for power generation in the steam turbine 4, resulting in surplus steam. Further, the boiler 2 is operated in a subcritical state, and saturated drain continuously flows into the water drain separator 31.

When the control device 80 receives an instruction to perform heat storage operation, it opens the heat storage steam flow rate control valve 54, the heat storage drain flow rate control valve 56, and the low temperature water flow rate control valve 50. As a result, as shown by the thick line in FIG. Supplied. Further, all or part of the saturated drain flowing out from the water drain separator 31 is supplied to the hot water heater 51 via the heat storage drain line 57 and the heat storage drain flow control valve 56. Furthermore, as shown by the bold line in FIG. 3, all or part of the condensate supplied from the condensate pump 14 is supplied to the hot water heater as low temperature water via the low temperature water supply line 49 and the low temperature water flow rate control valve 50. 51.

In the hot water heater 51, incoming main steam and saturated drain are brought into contact with low temperature water to generate hot water at about 140°C. The amounts of main steam and saturated drain that flow in are uniquely determined by the operating conditions of the boiler 2 and the steam turbine 4. By controlling the low temperature water flow rate control valve 50, the control device 80 always controls the low temperature water flow rate so that the temperature of the high temperature water at the outlet of the hot water heater 51 is approximately 140°C. Further, the control device 80 constantly controls the water level of the hot water heater 51 by controlling the first high temperature water pump 52A. Note that if the main steam pressure or the water level of the water drain separator 31 rises temporarily due to changes in the operating state of the boiler 2, the control device 80 closes the turbine bypass valve 8 and the water drain separator drain control valve 32. is opened and discharges excess steam and saturated condensate to the condenser 13 through these control valves. Thereby, the hot water heater 51 can maintain constant operation.

The high temperature water supplied from the first high temperature water pump 52A is stored in the high temperature water tank 53. The heat storage operation is completed when the high temperature water tank 53 becomes full or when the low load operation of the thermal power plant 1 ends. The control device 80 monitors the water level of the high-temperature water tank 53, and when it determines that the water is full or receives a signal indicating that the low-load operation has ended, the control device 80 closes the heat storage steam flow rate control valve 54 and the heat storage drain. The flow control valve 56 and the low temperature water flow control valve 50 are closed. The water level of the high temperature water tank 53 is acquired from a water level sensor provided in the high temperature water tank 53.

While the high-temperature water is stored in the high-temperature water tank 53, a considerable amount of water is transferred from the low-temperature water tank 59 to the makeup water line 60, as shown by the thick line in FIG. is supplied to the container 13.

Note that when the steam turbine 4 is in a low-load operation where the output of the steam turbine 4 is around 5% of the rated load, the control device 80 controls the operation of the second high-pressure feed water heater 21 and the second high-pressure feedwater heater 21 from the high-pressure turbine 4A, intermediate-pressure turbine 4B, and low-pressure turbine 4C. Control is performed to cut off the air bleed to the high-pressure feed water heater 20 and low-pressure feed water heater 16. This is because, during low-load operation, sufficient pressure cannot be obtained in each steam turbine 4 to force the saturated condensate generated in each feedwater heater to the deaerator or condenser.

Furthermore, when the steam turbine 4 is in low-load operation, the main steam temperature at the inlet of the high-pressure turbine 4A and the reheated steam temperature at the inlet of the intermediate-pressure turbine 4B are adjusted as appropriate to avoid a situation in which the exhaust steam of the low-pressure turbine 4C enters a dry region. There is a need. For this purpose, desuperheaters may be installed in the main steam line 6 and reheat steam line 9 at the outlet of the boiler 2, respectively, and a cooling spray may be supplied.

If the low-load operation of the thermal power plant 1 cannot be ended even if the high-temperature water tank 53 is full, and the main steam from the boiler 2 and the saturated drain from the water drain separator 31 continue to be in surplus, By supplying the water to the condenser 13 via the turbine bypass line 7 and the water drain separator drain line 33, it is possible to continue the low-load operation of the thermal power plant 1. However, at that time, the heat of the steam and drain that have flowed into the condenser 13 will be released to the condenser cooling medium such as seawater.

<Heat dissipation operation>
FIG. 4 shows the heat dissipation operation of the thermal power plant 1, that is, the release form of high-temperature water during high-load operation. High load operation here generally refers to operation at 30% or more of the rated load of a thermal power plant.

Upon receiving the instruction for heat radiation operation, the control device 80 operates the second high temperature water pump 52B. Thereby, the high temperature water stored in the high temperature water tank 53 is supplied to the condensate line 15 by the second high temperature water pump 52B, and flows into the deaerator 17. In this case, the condensate from the condenser 13 is heated by the low-pressure feed water heater 16 via the condensate line 15 and then supplied to the deaerator 17 together with high-temperature water, as shown by the thick broken line in FIG. Alternatively, all or part of the condensate may be stored in the low temperature water tank 59 via the low temperature water storage line 58.

During heat dissipation operation, the supply of extracted air from the low pressure turbine 4C to the low pressure feed water heater 16 under high load operation is stopped (cut) to increase the output of the generator 5 or reduce the fuel consumption of the boiler 2. Realize. Specifically, when the steam turbine 4 is in a high-load operating state, the control device 80 switches all or a portion of the condensate flowing into the deaerator 17 to high-temperature water. Accordingly, the amount of condensed water passing through the low-pressure feedwater heater 16 is reduced or cut off, so that the bleed air supplied from the low-pressure turbine 4C to the low-pressure feedwater heater 16 is reduced or cut. As a result, the steam turbine 4 can operate with an increased output corresponding to the reduction in extracted air, and the output of the generator 5 can be increased. At this time, if increased power operation is not required in the main operating state, the main steam flow rate from the boiler 2 is reduced to keep the load on the steam turbine 4 constant, and the fuel consumption in the boiler 2 is also reduced. good.

Note that when the operating load is low and the internal temperature of the deaerator 17 decreases to below the high temperature water temperature, it is necessary to reduce the temperature of the water flowing into the deaerator 17 in accordance with the internal temperature of the deaerator 17. There is. In such a case, the condensate is sent via the low pressure feed water heater 16 and mixed with high temperature water supplied from the high temperature water tank 53.

The heat radiation operation ends when the water level of the high temperature water tank 53 reaches the lowest water level. That is, the control device 80 monitors the water level of the high temperature water tank 53 during heat dissipation operation, and stops the second high temperature water pump 52B when the water level reaches a predetermined lowest water level. Thereby, the thermal power plant 1 shifts to normal plant operation. In addition, in normal plant operation, the high temperature water supply via the second high temperature water pump 52B is stopped, and the low temperature water supply from the outlet of the condensate pump 14 to the low temperature water tank 59 is also stopped, and the total amount of condensate is The water is supplied to a deaerator 17 via a low pressure feed water heater 16.

<Water heat storage system>
FIG. 5 is an explanatory diagram of the additional installation range when the water heat storage system 70 is added to the thermal power plant 1. The additional installation range of the water heat storage system 70 is the range illustrated by the thick line in the figure. As described above, the water heat storage system 70 mainly includes the hot water heater 51, the high temperature water tank 53, the low temperature water tank 59, and the high temperature water pump 52. By adding the water heat storage system 70 to the existing thermal power plant 1 by utilizing the vacant space on the site, construction costs can be reduced.

Next, the general specifications of the water heat storage system 70 in a 1000 MW class coal-fired unit are illustrated below. Note that the low-temperature water tank 59 has a water storage capacity that is equal to or greater than the water storage capacity of the high-temperature water tank 53. This is so that when the high temperature water stored in the high temperature water tank 53 is supplied to the water supply line, the low temperature water tank 59 can store condensate in an amount corresponding to the supply amount.
Hot water heater: Direct contact type feed water heater High temperature water tank capacity: 5 x 3300m3 (0.3MPa) Total 16500m3
Low temperature water tank capacity: 2 x 8300m3 (atmospheric pressure) total 16600m3
Heat storage time: Approximately 6.0 hours Heat radiation time: Approximately 5.0 hours (100% ECR)

According to the above specifications, in the case of a 1000 MW class coal-fired unit, when the boiler is operated at a minimum load of 15%, the heat of steam and saturated drain equivalent to 10% load (100 MW), excluding 5% (50 MW) of the in-house power, is stored. However, parallel non-transmission operation (external power transmission 0% operation) with inertia remaining is possible.

The water heat storage system 70 is of a type that returns the stored heat together with the heat medium to the deaerator 17, so that substantially all of the heat can be recovered within the cycle. Heat exchange loss between the heat medium and water and/or steam, which must be considered in molten salt heat storage or metal PCM heat storage, does not need to be considered in water heat storage. However, it is necessary to take into account heat dissipation during storage in the high-temperature water tank 53 and heat loss due to piping warming at the start of heat storage (3 to 5%, depending on the time until heat dissipation). Note that due to the limit on the amount of water that can be supplied to the deaerator 17 during heat dissipation (limit on mass balance), the heat storage time is approximately 6.0 hours, whereas the heat dissipation time is approximately 5.0 hours at 100% ECR. becomes.

The operational images of a conventional plant assuming daytime DSS operation and the thermal power plant 1 of this embodiment, which is a coal-fired thermal power plant equipped with a water heat storage system 70, will be compared. It is assumed that three units, plants A, B, and C, are connected to the system. The following is an example of an assumed operation during a time period (for example, daytime) when renewable energy is generating a large amount of electricity and surplus electricity is generated.
<Conventional plant>
Plant A: Minimum load 15% operation (5% internal power, 10% power transmission)
Plant B: DSS operation (plant temporary stop, restart)
Plant C: DSS operation (plant temporary stop, restart)
Total power transmission amount: equivalent to 10% load <Thermal power plant of this embodiment>
Plant A: Parallel non-transmission operation (minimum load 15% operation (5% internal power, 10% heat storage))
Plant B: Parallel non-transmission operation (minimum load 15% operation (5% internal power, 10% heat storage))
Plant C: Parallel non-transmission operation (minimum load 15% operation (5% internal power, 10% heat storage))
Total power transmission amount: No power transmission (0% load)

As mentioned above, in the case of a conventional plant, one plant (here, plant A) is operated at 15% of the minimum load, and the remaining two plants (B and C) are operated under DSS. Even in that case, 10% of the power will be transmitted to the grid. On the other hand, the thermal power plant 1 of this embodiment is capable of parallel non-transmission operation in all the thermal power plants.

That is, by using the thermal power plant 1 of this embodiment, the amount of power transmitted can be reduced to the point where no power is transmitted to all three plants. This allows us to avoid DSS operation while increasing the amount of renewable energy we receive. Furthermore, in the thermal power plant 1 of this embodiment, by dissipating the stored heat during peak demand hours (for example, in the evening), fuel consumption can be reduced (about 3 to 4%) during peak demand hours. becomes possible.

The advantages of introducing the water heat storage system 70 of this embodiment into the thermal power plant 1 are as follows.
(1) Contributing to expanding the introduction of renewable energy By reducing the minimum plant load, it becomes possible to expand the capacity to accept renewable energy while maintaining system inertia.
(2) Reducing plant startup costs through low-load continuous operation By performing low-load continuous operation using cheap coal, it is possible to significantly reduce the cost of starting diesel oil, which is unavoidable in DSS operation.
(3) Avoiding equipment wear and tear and startup troubles due to DSS operation By operating the power generation unit continuously, various risks associated with DSS operation can be avoided.
(4) Responding to sudden load increase requests, etc. Since the generator 5 operates continuously at an extremely low load while maintaining grid parallelism, it is possible to respond to sudden load increase requests due to sudden accidents, etc. .
(5) Heat recovery during plant startup It becomes possible to recover and use heat that was previously discarded as startup loss.

As explained above, the thermal power plant 1 of this embodiment is equipped with the water heat storage system 70, and during low-load operation, the main steam corresponding to the difference between the steam generated from the boiler 2 and the steam consumed in the steam turbine 4 is The heat of the saturated drain is stored as high-temperature water in the high-temperature water tank 53. Further, during high-load operation, the stored high-temperature water is supplied to the deaerator 17.

As a result, the thermal power plant 1 of the present embodiment can reduce the heat equivalent to the difference even if the operating load of the generator 5 (steam turbine 4) is reduced from the minimum load of the boiler 2 during low-load operation. , can be stored as high temperature water. That is, during low-load operation, the operating load of the generator 5 (steam turbine 4) can be reduced from the minimum load of the boiler 2 without waste. As a result, it is possible to reduce the system power output from the thermal power plant 1 over a long period of time. Furthermore, during low-load operation, the power sent from the coal-fired power plant to the power grid can be reduced to almost 0% load (parallel non-transmission operation).

Further, by supplying the high-temperature water stored during low-load operation to the deaerator 17 during high-load operation, the load on the low-pressure feed water heater 16 can be reduced. Thereby, during high-load operation, low-pressure extraction air from the steam turbine 4 can be reduced or cut. Then, the output of the steam turbine 4 can be increased by the amount of heat of the reduced or cut low-pressure extracted air. Alternatively, when maintaining the output of the steam turbine 4, the flow rate of steam from the boiler 2 can be reduced by an amount corresponding to the amount of heat of the reduced or cut low-pressure extracted air, and as a result, the amount of fuel input to the boiler 2 can be reduced.

That is, according to the present embodiment, by reducing the operating load of the generator 5 (steam turbine 4) in the thermal power plant below the boiler minimum load and reducing the amount of power transmitted to the plant, high operability can be maintained while regeneration can be achieved. It is possible to provide thermal power generation technology that can flexibly respond to changes in the amount of energy generated.

<Modification 1>
In addition, in the above embodiment, the thermal power plant 1 has been described as an example in which the thermal power plant 1 is provided with one each of the low-pressure feed water heater 16 and the second high-pressure feed water heater 21. Good too.

FIG. 8 shows a configuration example in which the thermal power plant 1 includes four low-pressure feedwater heaters 16 and two second high-pressure feedwater heaters 21.

In this case, the extracted steam extracted from each steam turbine 4 and a portion of the exhaust steam exhausted from each steam turbine 4 are supplied to different locations depending on their temperature.

For example, the high pressure extracted steam hb of the high pressure turbine 4A is supplied to the second high pressure feed water heater 21 on the downstream side. The saturated drain (condensed high-pressure extracted steam hb) discharged from the second high-pressure feedwater heater 21 on the downstream side is supplied to the second high-pressure feedwater heater 21 on the upstream side. A part of the high pressure exhaust steam he of the high pressure turbine 4A is supplied to the second high pressure feed water heater 21 on the upstream side. Saturated drain (condensed high-pressure extracted steam hb and high-pressure exhaust steam he) discharged from the second high-pressure feedwater heater 21 on the upstream side is supplied to the first high-pressure feedwater heater 20. The intermediate pressure extracted steam ib of the intermediate pressure turbine 4B is supplied to the first high pressure feed water heater 20. Saturated drain (condensed from high-pressure extracted steam hb, intermediate-pressure extracted steam ib, and high-pressure exhaust steam he) discharged from the first high-pressure feedwater heater 20 is supplied to the deaerator 17. A part of the intermediate pressure exhaust steam ie of the intermediate pressure turbine 4B is supplied to the deaerator 17. The extracted steam (lb1, lb2, lb3, lb4) of the low-pressure turbine 4C is supplied from the downstream side of each low-pressure feedwater heater 16 in descending order of temperature. The saturated condensate (condensed bleed steam) discharged from each low pressure feed water heater 16 is supplied to the low pressure feed water heater 16 upstream of each low pressure feed water heater 16 . Saturated drain (condensed from extracted steam lb1, lb2, lb3, lb4) discharged from the most upstream low-pressure feedwater heater 16 is supplied to the condenser 13.

As a result, steam can be supplied to the optimal feed water heater according to the steam temperature, allowing efficient operation without waste.

<Modification 2>
Further, in the above-described embodiment and modification 1, during heat dissipation operation, the confluence point of high-temperature water supplied from the high-temperature water tank 53 is provided on the exit side of the lowest-pressure feed water heater 16 at the lowest downstream. For example, when a plurality of low-pressure feed water heaters 16 are provided, a plurality of merging points may be provided and switching may be performed depending on the temperature of the high-temperature water.

In this modification, a confluence point where high-temperature water from the high-temperature water tank 53 joins the condensate line 15 is provided on the outlet side of each low-pressure feed water heater 16. The temperature of the condensate supplied by the condensate pump 14 increases as it passes through the low-pressure feedwater heater 16. In this modification, high-temperature water is merged at a confluence point that does not lower the temperature of the condensate on the outlet side of the low-pressure feed water heater 16.

To achieve this, the control device 80 monitors the temperature of the high-temperature water, and when the high-temperature water temperature decreases, the confluence point is sequentially switched to the low-temperature side (low-pressure feed water heater 16 one step upstream). The switching to the low temperature side of the confluence point is performed, for example, when the temperature of the high temperature water flowing out from the high temperature water tank 53 becomes lower than the outlet temperature of each low pressure feed water heater 16 for a certain period of time.

Hereinafter, as in Modification 1, an example will be given in which four low-pressure feed water heaters 16A, 16B, 16C, and 16D are provided in series on the condensate line 15 downstream of the condensate pump 14 in order from the downstream side. Please explain in detail. FIG. 9 shows only the relevant parts extracted.

As shown in this figure, in this modification, the thermal power plant 1 includes a high-temperature water merging line 71 that merges high-temperature water in a high-temperature water tank 53 with a condensate line 15, and a temperature sensor that measures the temperature of condensate. It includes 72A, 72B, 72C, 72D, and 72E, switching valves 73A, 73B, 73C, 73D, 73E, and 73F, and a flow rate control valve 76. Further, the high temperature water confluence line 71 includes three branch points 74A, 74B, and 74C. Further, the high-temperature water confluence line 71 converges at confluence points 75A, 75B, 75C, and 75D provided on the exit sides of the low-pressure feed water heaters 16A, 16B, 16C, and 16D, respectively.

In addition, below, when there is no need to distinguish, the low pressure feed water heater 16, the temperature sensor 72, the switching valve 73, the branch point 74, and the confluence point 75 are respectively represented.

The branch point 74A is a branch point where the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16A branches off from the high-temperature water confluence line 71 toward the low-pressure feed water heaters 16B, 16C, and 16D. The branch point 74B is a branch point where the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16B branches off from the high-temperature water confluence line 71 toward the low-pressure feed water heaters 16C and 16D. The branch point 74C is a branch point where the high-temperature water confluence line 71 toward the low-pressure feed water heater 16D branches from the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16C.

Temperature sensors 72A, 72B, 72C, and 72D are provided near the outlets of the low-pressure feed water heaters 16A, 16B, 16C, and 16D, respectively, and measure the temperature of condensate near the outlets. The temperature sensor 72E is provided between the outlet of the high-temperature water tank 53 and the branch point 74A, and measures the temperature of the high-temperature water supplied from the high-temperature water tank 53. In this figure, it is provided between the second high temperature water pump 52B and the branch point 74.

Moreover, the switching valve 73A is provided between the branch point 74A and the confluence point 75A, and controls the flow of high-temperature water into the confluence line 71 toward the outlet of the low-pressure feed water heater 16A. The switching valve 73B is provided between the branch point 74B and the confluence point 75B, and controls the flow of high-temperature water into the confluence line 71 toward the outlet of the low-pressure feed water heater 16B. The switching valve 73C is provided between the branch point 74C and the confluence point 75C, and controls the flow of high-temperature water into the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16C. The switching valve 73D is provided between the branch point 74C and the confluence point 75D, and controls the flow of high-temperature water into the confluence line 71 toward the outlet of the low-pressure feed water heater 16D. The flow rate control valve 76 is provided downstream of the second high temperature water pump 52B and controls the flow rate of high temperature water.

The control device 80 receives temperature information from each temperature sensor 72 at predetermined time intervals, and includes the high temperature water temperature received from the temperature sensor 72E, the outlet temperature received from each temperature sensor 72A, 72B, 72C, and 72D, are compared in order, and the merging point is switched depending on the result.

Here, the flow of the merging point switching process by the control device 80 will be explained. FIG. 10 is a processing flow of the merging point switching process of this modification.

Note that here, both the confluence point and the low-pressure feed water heater 16 are numbered sequentially from the downstream side. Further, it is assumed that N (N is an integer greater than or equal to 1) number of confluence points and low-pressure feed water heaters 16 are provided. Further, n is a counter. The "fixed time" for making the switching decision is set to T1. Further, it is assumed that the temperature of the high-temperature water and the temperature on the outlet side of the low-pressure feed water heater 16 are measured at predetermined time intervals.

The control device 80 first initializes a counter (n=1) and initializes a time counter Δt (Δt=0) (step S1001).

First, the control device 80 sets the first merging point to the merging point to be used (referred to as the used merging point) (step S1002), and sets each switching valve 73 so that the high temperature water joins at the used merging point. control.

Next, the control device 80 acquires the high temperature water temperature TH and the outlet side temperature TLn of the nth low pressure water heater 16 (comparison target heater) (step S1003).

The control device 80 determines whether the obtained high temperature water temperature TH is less than the outlet side temperature TLn (step S1004), and if the high temperature water temperature TH is equal to or higher than the outlet side temperature TLn (No), initializes the aging counter Δt. (step S1009), and the process returns to step S1003.

On the other hand, if the high temperature water temperature TH is less than the outlet side temperature TLn (Yes), the control device 80 determines whether or not this state has elapsed for a certain period of time T1 (step S1005). If the time has not passed yet (No), the process returns to step S1003.

On the other hand, if a certain period of time has elapsed (Yes), the control device 80 switches the confluence point in use to the confluence point provided on the outlet side of the low-pressure feed water heater 16 one stage upstream (step S1006), and after switching Each switching valve 73 is controlled so that the high-temperature water joins at the usage junction.

After that, the control device 80 increments the counter n by 1, initializes the time counter Δt (step S1007), and determines whether the used confluence point has become the most upstream confluence point (n=N?) (step S1007). S1008). If the confluence point set as the used confluence point is not the most upstream confluence point, the process returns to step S1003 and repeats the process. On the other hand, if the most upstream merging point is set as the used merging point, the process ends immediately.

The above-mentioned merging point switching process will be explained using a specific example. First, the control device 80 compares the high temperature water temperature with the outlet temperature (TLA) acquired by the temperature sensor 72A. When the high temperature water temperature is equal to or higher than the outlet temperature TLA, the control device 80 opens the switching valve 73A and closes the switching valves 73B, 73C, and 73D. Thereby, the high temperature water joins the condensate line 15 at the confluence point 75A, that is, at the outlet side of the low pressure feed water heater 16A.

If the high temperature water temperature continues to be lower than the outlet temperature TLA for a certain period of time, the control device 80 compares the high temperature water temperature with the outlet temperature (TLB) acquired by the temperature sensor 72B. When the high temperature water temperature is equal to or higher than the outlet temperature TLB, the control device opens the switching valve 73B and closes the switching valves 73A, 73C, and 73D. Thereby, the high temperature water joins the condensate line 15 at the confluence point 75B, that is, between the outlet of the low pressure feed water heater 16B and the inlet of the low pressure feed water heater 16A.

When the high temperature water temperature remains lower than the outlet temperature TLB for a certain period of time, the control device 80 compares the high temperature water temperature with the outlet temperature (TLC) acquired by the temperature sensor 72C. When the high temperature water temperature is equal to or higher than the outlet temperature TLC, the control device 80 opens the switching valve 73C and closes the switching valves 73A, 73B, and 73D. Thereby, the high temperature water joins the condensate line 15 at the confluence point 75C, that is, between the outlet of the low pressure feed water heater 16C and the inlet of the low pressure feed water heater 16B.

When the high temperature water temperature remains below the outlet temperature TLC for a certain period of time, the control device 80 opens the switching valve 73D and closes the switching valves 73A, 73B, and 73C. Thereby, the high temperature water joins the condensate line 15 at the confluence point 75D, that is, between the outlet of the low pressure feed water heater 16C and the inlet of the low pressure feed water heater 16B.

Note that the control device 80 may be configured to start controlling the switching valve 73 when the temperature of the high-temperature water supplied from the high-temperature water tank 53 becomes less than a predetermined threshold. Specifically, when the temperature of the high-temperature water supplied from the high-temperature water tank 53 drops from 140°C to 100°C, the above-described confluence switching process is started.

In addition, in this modification, the high temperature water temperature and the outlet temperature of each low pressure feed water heater 16 are compared in order from the downstream side of the low pressure feed water heater 16, and the switching valve 73 is controlled. is not limited to this. For example, controller 80 may compare the high temperature water temperature and the outlet temperature of all low pressure feed water heaters 16 to determine the confluence point to use. In this case, each switching valve 73 is controlled so that the high-temperature water joins at a confluence point 75 on the outlet side of the low-pressure feed water heater 16, which has an outlet temperature lower than the high-temperature water temperature and closest to the high-temperature water temperature.

In addition, in the example of FIG. 9, when the high temperature water temperature is less than the outlet temperature of the low pressure feed water heater 16C, even if it is less than the outlet temperature of the low pressure feed water heater 16D, it is made to merge at the confluence point 75D. For example, a merging point may be further provided on the inlet side of the low-pressure feed water heater 16D, and when the high temperature water temperature is lower than the outlet temperature of the low-pressure feed water heater 16D, control may be performed such that the water merges at the merging point. In this case, since the number of merging points is N+1, it is determined in step S1008 of the processing flow of the merging point switching process shown in FIG. 10 whether n=N+1.

According to this modification, when the high-temperature water in the high-temperature water tank 53 is made to join the condensate line 15 during heat dissipation operation, the joining point is changed depending on the temperature. That is, the high-temperature water is combined at the outlet side of the low-pressure feed water heater 16, which has an outlet temperature lower than the high-temperature water temperature and closest to the high-temperature water temperature. Thereby, the temperature of the condensate heated by the low-pressure feed water heater 16 is not lowered by the high-temperature water to be combined, and the low-pressure feed water heater 16 and the high-temperature water can be efficiently utilized.

<Modification 3>
In the above embodiment, the high temperature water generated in the hot water heater 51 is stored in the high temperature water tank 53 during heat storage operation. In this modification, a portion of the high-temperature water generated in the hot water heater 51 is controlled to be supplied to the deaerator 17 instead of the high-temperature water tank 53.

During heat storage operation, the steam turbine 4 is operated at an extremely low load, so that the extraction air for the purpose of heating the feed water is cut off, and the heating steam for the deaerator 17 may be supplied from the auxiliary steam system at the same time. This is because even during low load operation, it is necessary to maintain the exhaust gas temperature of the boiler 2 above a certain temperature, and it is essential to degas the feed water. Note that in this operating state, the temperature of the condensate flowing into the deaerator 17 decreases as the low pressure feed water heater 16 bleeds off the air, so it is necessary to increase the amount of auxiliary steam to compensate for this. In this modification, the decrease in the temperature of condensate flowing into the deaerator 17 due to the cut of the bleed air is compensated for by supplying the outlet water of the hot water heater 51. Thereby, an increase in auxiliary steam consumption of the thermal power plant 1 can be suppressed.

FIG. 11 shows parts of the thermal power plant 1 related to this modification. As shown by the thick dotted line in this figure, in this modification, a portion of the high temperature water generated by the hot water heater 51 is supplied to the deaerator 17 during heat storage operation.

Note that during heat storage operation, water may be continuously supplied from the hot water heater 51 to the deaerator 17 for a predetermined amount. Further, when the temperature of the condensate supplied to the deaerator 17 decreases, control may be performed so that the condensate is supplied.

In the latter case, the thermal power plant 1 includes a temperature sensor 72 and a flow control valve 76. The temperature sensor 72 measures the temperature of condensate on the outlet side of the low-pressure feedwater heater 16 and is provided on the outlet side of the low-pressure feedwater heater 16 . The flow rate control valve 76 controls the supply of high-temperature water from the hot water heater 51 to the deaerator 17, and is provided on the high-temperature water confluence line 71 that connects the high-temperature water tank 53 and the condensate line 15. It will be done.

The control device 80 acquires temperature data measured by the temperature sensor 72 at predetermined time intervals, and when the temperature data is less than a predetermined threshold, issues an instruction to open the flow control valve 76 and heats the high-temperature water. from the container 51 to the deaerator 17.

As a result, the high-temperature water from the hot water heater 51 is mixed with condensate and supplied to the deaerator 17, making it possible to increase the temperature of the condensate flowing into the deaerator and reducing auxiliary steam consumption. It can be suppressed.

In addition, the above operation is particularly useful when remodeling an existing unit where the size of the auxiliary steam line piping is limited due to layout, or when it is desired to avoid unnecessary increases in the diameter of the auxiliary steam line piping when installing a new unit. be. In addition, instead of supplying condensate water to the hot water heater 51 and water supply to the deaerator 17 independently, a part of the high-temperature water is diverted to the water supply to the deaerator 17, so that the existing unit When remodeled, it becomes possible to operate within the capacity of the condensate pump 14 and the condensate desalination device. When a new unit is installed, it is also possible to design the capacity of the pump and equipment to simultaneously supply condensate to the hot water heater 51 and water to the deaerator 17. However, in view of the fact that costs are expected to increase due to an increase in the capacity of pumps and equipment, it is desirable to divert some of the high-temperature water to the water supply to the deaerator 17, as in the case of remodeling the existing unit.

<Modification 4>
In the above embodiment, two high-temperature water tanks 53 and low-temperature water tanks 59 are provided, and during heat storage, high-temperature water is stored in the high-temperature water tank 53, and during heat dissipation, high-temperature water after use is transferred to the low-temperature water tank 59. to be stored. However, the configuration is not limited to this. For example, one thermocline tank 61 may be provided to have the functions of the high temperature water tank 53 and the low temperature water tank 59.

The thermocline tank 61 is a single tank that includes a high-temperature water section, a low-temperature water section, and a thermocline in one tank, and is capable of storing high-temperature water and low-temperature water. The high-temperature water section is located at the top of the tank, the low-temperature water section is located at the bottom of the tank, and the high-temperature water section and the low-temperature water section are separated by a thermocline.

FIG. 12 shows locations of the thermal power plant 1 related to this modification. As shown in this figure, the thermocline tank 61 includes a high-temperature water inlet and outlet through which high-temperature water is supplied and drained, and a low-temperature water inlet and outlet through which low-temperature water is supplied and discharged.

As shown by thick lines in FIG. 12, a high-temperature water supply line 64 that supplies hot water from the hot water heater 51 and a high-temperature water merging line 71 are connected to the high-temperature water inlet/outlet. On the other hand, a low temperature water return line 62 connected to the condenser 13 and a second low temperature water supply line 63 branched from the low temperature water supply line 49 are connected to the low temperature water inlet/outlet.

During heat storage operation, in the embodiment described above, condensate is supplied from the condenser 13 to the hot water heater 51, and high temperature water is generated in the hot water heater 51 and stored in the high temperature water tank 53. While condensate is being supplied from the condenser 13 to the hot water heater 51, water in an amount equivalent to the supplied condensate is supplied from the low-temperature water tank 59 to the condenser 13.

In this modification, as in the above embodiment, high temperature water is supplied from the condenser 13 to the hot water heater 51, high temperature water is generated in the hot water heater 51, and the high temperature water is passed through the high temperature water supply line 64 to the thermocline tank 61. stored in the department. However, in this modified example, as shown by the thick broken line in FIG. The water is supplied to the water container 13. Further, as shown by the dotted line, water is partially passed from the hot water heater 51 to the deaerator 17.

Further, during heat dissipation operation, in the above embodiment, high temperature water is supplied from the high temperature water tank 53 to the deaerator 17, and the condensate in the condenser 13 is converted into low temperature water via the low temperature water storage line 58. It is stored in the tank 59. On the other hand, in this modification, when high-temperature water is supplied from the high-temperature water section of the thermocline tank 61 to the deaerator 17, as shown by the thick line in FIG. The water is supplied from the condenser 13 to the low temperature water section of the thermocline tank 61 via a second low temperature water supply line 63 branched downstream from the condensate pump 14 of the condensate line 15 .

In this modification, the capacity of the thermocline tank 61 is the required capacity of the high-temperature water tank 53 or the low-temperature water tank 59 plus the volume corresponding to the thermocline, which does not contribute to the tank capacity, so that it is always operated in a full state. Ru.

According to this modification, by using the thermocline tank 61, it is possible to save space related to tank installation, which is particularly effective when there are restrictions on the power generation site. Furthermore, if the thermocline tank 61 is inexpensive, the cost can be reduced compared to installing individual tanks.

In addition, the thermocline tank 61 has a structure that can withstand the saturation pressure of high-temperature water, and in order to avoid mixing of high-temperature water and low-temperature water in the tank and to allow each to be taken in and out, the high-temperature water in the thermocline tank 61 is The line configuration and operation thereof connected to the high temperature water tank 53 and the low temperature water tank are the same as in the case where the high temperature water tank 53 and the low temperature water tank 59 are installed separately.

<Modification 5>
In the embodiment described above, a case is described in which a supercritical boiler is used as the boiler 2 in a supercritical state except under low load conditions, but the boiler type is not limited to this. For example, a subcritical boiler that is operated in a subcritical state under all loads may be used.

The subcritical boiler includes a steam drum 34, a continuous blow tank 37, a flash tank 38, and an intermittent blow line 39 instead of the water drain separator 31, as shown by the thick line in FIG.

The steam drum 34 separates steam and saturated water (saturated drain). The separated steam flows into the superheater 36 and the saturated drain flows into the continuous blow tank 37, respectively. The saturated condensate passes through brackish water separation and steam recovery in a continuous blow tank 37 before flowing into a flash tank 38 . The intermittent blow line 39 provided in the steam drum 34 is used to avoid an increase in drum level due to boiler water swelling at startup and to blow boiler water when the boiler water quality deteriorates.

Note that a part of the saturated drain that has flowed into the continuous blow tank 37 becomes flash steam, is supplied to the deaerator 17, and is used as part of the heated steam of the deaerator 17.

Note that when a subcritical drum is used, the heat storage drain line 57 branches from the intermittent blow line 39. During heat storage operation, all or part of the saturated drain separated by the steam drum 34 is supplied to the hot water heater 51 via the heat storage drain line 57 branching from the intermittent blow line 39 and the heat storage drain flow rate control valve 56. be done.

During heat storage operation, even in a subcritical boiler, as in the case of using a supercritical boiler, all or part of the surplus main steam in the main steam line 6 is transferred to the heat storage steam line 55 and the heat storage steam flow rate control valve 54. The hot water is supplied to the hot water heater 51 via the hot water heater 51. During heat storage operation, the hot water heater 51 uses this main steam and the saturated drain supplied from the steam drum 34 as heat sources, and generates high-temperature water from the condensed water supplied from the condenser 13.

In addition, in a subcritical boiler, the amount of drain extracted from the steam drum 34 is determined based on the amount of fuel input and the main steam flow rate. Level control of the steam drum 34 is performed by a drum level control valve. If the drum level rises temporarily due to changes in operating conditions, in addition to the drum level control valve, the intermittent blow valve is opened and closed as necessary.

That is, the control device 80 monitors the drum level, and when the drum level exceeds a predetermined threshold value for a certain period of time or more, the control device 80 lowers the opening degree of the drum level control valve and suppresses the amount of inflow water supply. Alternatively, an intermittent blow valve may be opened to draw out the saturated drain as an intermittent blow. The drum level is obtained from a water level sensor provided on the steam drum 34.

<Modification 6>
The heat source of the hot water heater 51 is not limited to turbine bypass steam. For example, it may be reheated steam passing through a reheated steam line, or it may be extracted air or exhaust air from each steam turbine 4.

Note that each modification may be combined. For example, the thermal power plant 1 of the above embodiment includes a plurality of low-pressure feed water heaters 16, a configuration in which the merging destination of the high-temperature water merging line 71 is switched depending on the temperature of the high-temperature water, a configuration that allows partial water passage, a high-temperature water tank 53, At least one of a configuration using a thermocline tank 61 instead of the low temperature water tank 59, a configuration using a subcritical boiler, and a configuration using various types of steam as the heat source of the hot water heater 51 may be provided.

1 Thermal power plant 2 Boiler 4 Steam turbine 4A High pressure turbine 4B Intermediate pressure turbine 4C Low pressure turbine 5 Generator 6 Main steam line 7 Turbine bypass line 8 Turbine bypass valve 9 Reheat steam line 10 Low pressure turbine bypass line 11 Low pressure turbine bypass valve 12 Medium pressure turbine exhaust line 13 Condenser 14 Condensate pump 15 Condensate line 16 Low pressure feed water heater 16A Low pressure feed water heater 16B Low pressure feed water heater 16C Low pressure feed water heater 16D Low pressure feed water heater 17 Deaerator 18 Feed water pump 19 Water line 20 First high pressure feed water heater 21 Second high pressure feed water heater 31 Water drain separator 32 Water drain separator drain control valve 33 Water drain separator drain line 34 Steam drum 35 Reheater 36 Superheater 37 Continuous blow tank 38 Flash tank 39 Intermittent blow line 49 Low temperature water supply line 50 Low temperature water flow rate control valve 51 Hot water heater 52 High temperature water pump 52A First high temperature water pump 52B Second high temperature water pump 53 High temperature water tank 54 Heat storage steam flow rate control valve 55 Heat storage steam line 56 Heat storage drain flow control valve 57 Heat storage drain line 58 Low temperature water storage line 59 Low temperature water tank 60 Make-up water line 61 Thermocline tank 62 Low temperature water return line 63 Second low temperature water supply line 64 High temperature water supply line 70 Water heat storage system 71 High temperature water Merging line 72 Temperature sensor 72A Temperature sensor 72B Temperature sensor 72C Temperature sensor 72D Temperature sensor 72E Temperature sensor 73A Switching valve 73B Switching valve 73C Switching valve 73D Switching valve 74 Branch point 74A Branch point 74B Branch point 74C Branch point 75 Confluence point 75A Confluence point 75B Confluence point 75C Confluence point 75D Confluence point 76 Flow rate control valve 80 Control device 81 Control console

Claims (12)

a boiler, a steam turbine driven by steam from the boiler, a turbine bypass line for sending steam bypassing the steam turbine, a condenser for cooling the exhaust of the steam turbine and generating condensate; A thermal power plant comprising: a low-pressure feed water heater that heats the condensate with extracted steam from the steam turbine; and a deaerator that degasses the condensate with the extracted steam,
a hot water heater that uses the main steam of the turbine bypass line as a heat source and uses the condensate supplied from the condenser as high-temperature water;
a high-temperature water tank that stores the high-temperature water;
a high-temperature water pump that sends the high-temperature water stored in the high-temperature water tank to the downstream of the low-pressure feed water heater or to the deaerator;
Equipped with
The boiler includes a steam drum that separates steam and saturated water,
The hot water heater is a thermal power generation plant in which intermittent blow from the steam drum is also used as the heat source. a boiler, a steam turbine driven by steam from the boiler, a turbine bypass line for sending steam bypassing the steam turbine, a condenser for cooling the exhaust of the steam turbine and generating condensate; A thermal power plant comprising: a low-pressure feed water heater that heats the condensate with extracted steam from the steam turbine; and a deaerator that degasses the condensate with the extracted steam,
a hot water heater that uses the main steam of the turbine bypass line as a heat source and uses the condensate supplied from the condenser as high-temperature water;
a high-temperature water tank that stores the high-temperature water;
a high-temperature water pump that sends the high-temperature water stored in the high-temperature water tank to the downstream of the low-pressure feed water heater or to the deaerator;
Equipped with
A plurality of the low pressure feed water heaters are provided in series in a condensate line that sends the condensate from the condenser to the deaerator,
A high-temperature water merging line for merging the high-temperature water at a merging point where the temperature of the condensate on the outlet side is least reduced among the plurality of low-pressure feed water heaters according to a high-temperature water temperature that is a temperature of the high-temperature water. Furthermore,
In the thermal power plant, the confluence points are provided in the condensate lines on the outlet side of the plurality of low-pressure feed water heaters, respectively. The hot water heater is a direct contact feed water heater that mixes the condensate and the main steam.
The thermal power plant according to claim 1 or 2 . The boiler includes a water drain separator that separates the mixed brackish water at the furnace outlet into brackish water,
The hot water heater also uses the saturated drain from which brackish water has been separated by the water drain separator as the heat source.
The thermal power plant according to claim 1 or 2 . The boiler includes a steam drum that separates steam and saturated water,
The hot water heater also uses intermittent blowing from the steam drum as the heat source.
The thermal power plant according to claim 2 . further comprising a low-temperature water tank that stores surplus water in the condenser for use as make-up water to the condenser, the low-temperature water tank having a water storage capacity equal to or greater than the water storage capacity of the high-temperature water tank;
The thermal power plant according to any one of claims 1 to 5 . The high-temperature water tank is a thermocline tank capable of storing the high-temperature water and low-temperature water with a thermocline in between, and supplies surplus water in the condenser to the condenser as the low-temperature water. Store water for make-up water,
The thermal power plant according to any one of claims 1 to 5 . A plurality of the low pressure feed water heaters are provided in series in a condensate line that sends the condensate from the condenser to the deaerator,
A high-temperature water merging line for merging the high-temperature water at a merging point where the temperature of the condensate on the outlet side is least reduced among the plurality of low-pressure feed water heaters according to a high-temperature water temperature that is a temperature of the high-temperature water. Furthermore,
The confluence point is provided in each of the condensate lines on the outlet side of the plurality of low-pressure feed water heaters,
The thermal power plant according to any one of claims 1 to 5 . A method for controlling a thermal power plant according to any one of claims 1 to 8 , comprising:
During low-load operation of the thermal power plant, the high-temperature water is generated using main steam corresponding to the difference between the steam generated by the boiler and the steam consumed by the steam turbine as the heat source, and stored in the high-temperature water tank;
A method for controlling a thermal power plant, comprising supplying the high-temperature water stored in the high-temperature water tank to the deaerator during high-load operation of the thermal power plant. The thermal power plant according to claim 9 , further comprising supplying a portion of the high-temperature water generated in the hot water heater to the deaerator according to the temperature of the deaerator during low-load operation of the steam turbine. How to control a power plant. The thermal power plant includes a plurality of low-pressure feed water heaters arranged in series in a condensate line that sends the condensate from the condenser to the deaerator, and also includes a plurality of low-pressure feed water heaters connected in series to the condensate line that sends the condensate from the condenser to the deaerator. Further comprising a merging point for merging the high-temperature water, which is provided in each of the condensate lines on the outlet side of the low-pressure feed water heater,
10. During high-load operation of the thermal power plant, the high-temperature water is merged at a confluence point that minimizes the temperature drop of the condensate on the outlet side among the plurality of low-pressure feed water heaters, depending on the temperature of the high-temperature water . Or the method for controlling a thermal power plant according to 10 . The most downstream low-pressure feed water heater of the plurality of low-pressure feed water heaters is set as a comparison heater, and the merging point where the high-temperature water is merged is set at the merging point on the outlet side of the comparison target heater,
At predetermined time intervals, the temperature of the high temperature water is compared with the temperature of the condensate on the outlet side of the comparison target heater, and the temperature of the high temperature water is lower than the temperature of the condensate for a predetermined period. In this case, the merging point where the high temperature water is merged is switched to the outlet side of the low pressure feed water heater that is one step upstream of the comparison target heater, and the low pressure feed water heater one step upstream is switched to the comparison target heating. 12. The method of controlling a thermal power plant according to claim 11 , further comprising repeating the process of repeating the process.

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